3D cadastre implementationusing UAV-based photogrammetry methodwithout ground control points (GCPs)

Recently, cadastre has become a suitable platform for global partnership in management of land and its assets. Due to ever- increasing population, spatial organization of citiesis considered to be one of the most important issues in national development planning. This indicates the necessity of using 3D land information systems since theenvironment, quality, ownership and other benefits of lands do not only change horizontallyany moreand height is also a decisive and vital factor.Therefore, 3D cadastreis used as abasis for integrating information into a complete and efficient information storage system. This system is usedtomanage scarce land resources and plays a key role in achieving future legal and managerial success in the field ofreal-estate. Designing and implementing a system capable of displaying the third dimension (height) is very complex. Common methods of producing 3D cadastral models include land surveying, classical aerial photogrammetry, high-resolution satellite imagery, and so on. Recently, the advent of drones has provided a suitable platform for large-scale cadastral mapping. Collecting high resolution images, processing withstructure from motion(SFM) method, multi-stereo vision (MSV), and dense 3D point cloud with a high resolution of about a few centimeters are the main advantages of these tools. Recentstudies in this field indicate high capabilities of UAV-based photogrammetry method for the production and updating of cadastral maps.  

Due to the applied nature of the present study, guideline for the spatial information production using photogrammetric method published by Tehran Municipality and other Surveying and Mapping guidelines published by the National Cartographic Center of Iran have been used to produce 3D cadastral modeland reach relatively real results. The study area is Khosban village in MiyanTaleqan rural district, in the central district of Taleqan County, Alborz Province, Iran. Necessary information was collected using an eBee Plus survey drone with a SODA camera (designed for professional photogrammetric applications). Besides, exterior orientation parameters were measured using the preciseinertial measurement unit (IMU), global navigation satellite system (GNSS) Antenna withreal-time kinematic (RTK) and post-processing kinematic (PPK) techniques and triangulation was performed using these parameters. To increase the accuracy, reduce hidden areas and achieve more accurate 3D models, 75%longitudinal and transverse overlappingwere considered for the images. Image processing was performed using Pix4dmapper and Metashape software and products such as orthomosaic, dense 3D point cloud, and digital surface model were produced. To prove thegeometric accuracy of triangulation, 8 ground control points were used, and32 checkpoints were also used for the final evaluation of 3D models.  

3D cadastre implementation was performedin the present paperusing UAV based photogrammetry without any ground control points. According to the results of triangulation, the maximum root mean square error in the X-component was reported 3.21 cm, the Y-componentwas reported2.86 cm, and the Z-component was reported 3.96 cm using Pix4dmapper and Metashape software. Moreover, 32 sample checkpoints were used for the final evaluation of the 3D models and data collected from these points were compared with the reference data. Results indicated the occurrence of maximum root mean square error in the horizontal components (X, Y) of 0.2 and 0.21 meter respectively, and 0.27 meter in the height component (Z). A correlation coefficient of about 1 represents high geometric accuracy of the 3D models produced using UAV based photogrammetry.  

3D cadastre can be used as a tool for improving land management and related issues. Due to structural complexity and ownership issues,most developed countrieshave not yet fully implemented 3D cadastre. However, these countries are always looking for ways to achieve such a system. So far in our country, the issue of 3D cadaster has only been pursued in academic studies and no practical stephas been taken to implement this system. Unfortunately, technical dimension and preparation of 3D models are only a part of 3d cadastre and legal issues occurring due to insufficient understanding of the third dimensionand its complexity alsolead to failure in the implementation of 3D cadaster.